private void textBoxImpurity_TextChanged(object sender, EventArgs e)
 {
     saveButton.Enabled        = controller.checkSave(textBoxImpurity.Text);
     saveButton.BackColor      = controller.checkSave(textBoxImpurity.Text) ? Color.DarkOrange : Color.LightBlue;
     textBoxImpurity.BackColor = !AddlevelOfQualityController.isEmpty(textBoxImpurity.Text.Replace(" ", "")) ? Color.White : Color.LightBlue;
 }